Many olefin polymerization catalysts are known, including conventional Ziegler-Natta catalysts. While these catalysts are inexpensive, they exhibit low activity and are generally poor at incorporating α-olefin comonomers. To improve polymer properties, single-site catalysts, in particular metallocenes, are beginning to replace Ziegler-Natta catalysts.
Magnesium chloride-supported catalysts are known and the combination of alcohols with magnesium chloride is known for Ziegler-Natta catalysts (see, for example, U.S. Pat. Nos. 4,330,649, 4,421,674, 5,106,807, and 5,173,465 and references therein). Generally, alcohols are used to improve the stereospecificity in propylene polymerizations.
Catalyst precursors that incorporate a transition metal and an indenoindolyl ligand are known. U.S. Pat. Nos. 6,232,260 and 6,451,724 disclose the use of transition metal catalysts based upon indenoindolyl ligands, but they have no examples using supported catalysts. While they mention that supported catalysts may be used, magnesium chloride is not mentioned and little information is given about the preparation of the supported catalysts.
WO 01/53360 discloses open architecture indenoindolyl catalysts that may be supported. Magnesium halides are included in the listing of possible inert supports, but no further information is given. In the single example (Example 8) preparing a supported catalyst, a solution of the catalyst is added to a polyethylene support. There is no indication as to the suitability of a magnesium chloride-alcohol support.
U.S. Pat. No. 6,559,251 discloses a process for polymerizing olefins with a silica-supported, indenoindolyl Group 4–6 transition metal complex having open architecture. Magnesium chloride supports are not disclosed.
U.S. Pat. No. 6,541,583 discloses a process for polymerizing propylene in the presence of a Group 3–5 transition metal catalyst that has two non-bridged indenoindolyl ligands. None of the examples uses a supported catalyst. They state that the catalyst can be immobilized on a support and include magnesium chloride in a list of preferred supports, but they give no process details. There is no indication as to the suitability of a magnesium chloride-alcohol support.
U.S. Pat. No. 6,211,311 prepares supported catalysts containing heteroatomic ligands. The list of supports includes magnesium chloride. The support is chemically modified with an organoaluminum, organosilicon, organomagnesium or organoboron compound for improved catalyst stability and activity. There is no indication as to the suitability of a magnesium chloride-alcohol support.
Pending application Ser. No. 10/834,425, filed Apr. 29, 2004, discloses the polymerization of ethylene in the presence of a supported indenoindolyl complex having open architecture. Magnesium chloride is included in the list of preferred supports. No process details are given for magnesium chloride. Silica is the only support material used in the examples. There is no indication as to the suitability of a magnesium chloride-alcohol support.
U.S. Pat. No. 6,583,242 teaches a catalyst system which comprises a support having a mean particle size less than about 30 microns, wherein the support is chemically treated with an alumoxane and an organometallic complex containing at least one indenoindolyl ligand and an activator. All of the examples use silica as a support material. Magnesium chloride is listed as a preferred support material, but again, there is no indication as to the suitability of a magnesium chloride-alcohol support.
Despite the considerable work that has been done with supporting catalysts based upon indenoindolyl ligands, there is a need for improvement, especially with regard to increasing catalyst activity and improving polymer rheology. Magnesium chloride-alcohol supports have apparently not been used in conjunction with organometallic complexes that incorporate indenoindolyl ligands. Alcohols and other protic materials are generally considered to deactivate single-site catalysts, the opposite of the effect we have found when the magnesium chloride-alcohol supports are used with complexes containing indenoindolyl ligands.